[CMake] transitive linkage of OBJECT library targets

[Richard Szabo]

Hi cmakers

I'm trying to get the following example working:
```
cmake_minimum_required(VERSION 3.14)
project(test_object_lib_nesting)

set(CMAKE_CXX_STANDARD 14)

add_library(first_object_lib OBJECT first.cpp)

add_library(second_object_lib OBJECT second.cpp)

target_link_libraries(second_object_lib first_object_lib)

add_executable(test_object_lib_nesting main.cpp)

target_link_libraries(test_object_lib_nesting second_object_lib)
```

The problem I have that the linker command line will have only the
second.cpp.o for linking the first.cpp.o will not be added as link
object to the exe. Causing missing symbols on exe linkage.

How to transitively resolve and link "nested" Object library targets ?.